Propeller-type blower



June 10, 1930. H SCHMlDT 1,762,358

PROPELLER TYPE BLOWER Filed May 20, 1927 3 Sheets-Sheet l WITNESS INVENTOR (5.1%, .E5hmidl' BY @KTBM ATTORN EY June 10, 1930. 5 1,762 358 PROPELLER TYPE BLOWER Filed May 20, 1927 5 Sheets-Sheet 2 WITNESS F E dw Hi m5 BY I {ATTORNEY June W, 1930. H. F. SCHMIDT PROPELLER TYPE BLOWER 3 sheets-sheet 5 Filed May 20, 1927 wwwwwwwwwwwwwwmwwwwwwwwwwwwwww a A 5 s m M ATTORNEY Patent une 10, 193.0

HENRY F. SCHMIDT, OF LANSDO'WNE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC 8: MANUFACTURING COMPANY, A. CORPORATION. OF PENNSYLVANIA.

PROPELLEE-TYPE BLOWER Application filed May 20,

My invention relates to blowers, more particularly to that type suitable for marine boiler rooms, and it has for an object to provide a form of blower which shall very cffectively and very efliciently convert the velocity energy imparted to the air by the rotating element: of the blower into pressur energy.

It has for a further object to provide a blower which shall be so arranged that the air passing therethrough shall not be subjected to shock, in whichfrictional resistance to flow shall be reduced and in which eddy currents shall be minimized, thus insuring very efficient flow characteristics.

These and other objects, which will be made apparent throughout the further description of my invention, may be attained by the employment oi the apparatus hereinafter de- 0 scribed and illustratedin the accompanying drawings in which:

Fig. 1 is a view, in sectional elevation,

showing one form of blower arranged in ac- ,cordance with my invention;

Fig. 2 is a-view, in sectional elevation, of

another form of blower arranged in accordance with my invention;

Fig. 3 is a diagrammatic view illustrating the passage of steam between the blades of a steam turbine; p

. Fig. 4 is a diagrammatic view which illustrates the method employed in designing the turbine blades shown in Fig. 3; and,

Fig. 5 is a sectional, somewhat diagrammatic, view of a portion of a steam turbine which is equipped with a reversing chamber.

In the design and construction of blowers, and especially those of theforced draft type, it is highly desirable that the air passing through the blower casing travel in a path which is nearly as straight or direct as possible in order thatvery little of its kinetic energfi be absorbed. However, in view of the fact t at it is generally necessary toprovide a blower casing of such form as to be capable 1927. semi No. water.

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therefore, advisable to make the radius of this arcuate passage as large as possible or as nearly approaching a straight line as possi ble, in order that friction losses, etc., may be held to a minimum. llt is further desirable that the 'air passin through the annular, ,arcuate-shaped duct ow in a single, continuous curved'path and not in a path having its direction of curvature reversed, as reverse curvature of flow is conducive to frictional resistance.

Referring now to Fig. 1, I show a blower comprising a casing 10 havingan inlet portion 11 and a discharge portion 12. The casing 10 is adapted to be suspended from some su portin structure, such as the deck of a ship 13; T e casing 10 com rises a convergingportion 14, a cylindrica portion 15 and a diverging portion 16. Located within the cylindrical portion 15 is a propeller 17 having a. hub portion 18 a fish-tail portion 19'and a plurality of blades 21. The hub portion 18 and the fish-tail portion 19 are preferably stream-lined, as illustrated, in order to offer a minimum amount of resistance to the admission of air to the blower casing.

Disposed below and directly connected to the propeller 17 is a prime mover 22, such as a steam turbine, for driving the same. The

rime mover 22 is provided with a motive Enid admission valve 23 and an exhaust con nection 24. Interposed between the propeller 17 and the turbine 22 and directly connected to the latter is a central supporting member 25, which is provided with a plurality of fixed guide vanes 26 secured to the casm ]0 in order to support the propeller and t e turbine. While, in the present example, I have no shown the propeller and the turbine as being entirely supported from the casing 10, nevertheless, it is obvious that the propeller and the ity pressure conversion of the air dure ing its passage from the entrance 11 to the discharge 12. The outer contour of the central supporting member 25 is so formed, with respect to the casing 10, as to insure passage of the air'through a considerable s portion of the duct in a smooth, continuous curve which very nearly approaches a straight line. From inspection of the arrow lines shown in the right-hand portion of Fig. 1, which lines graphically represent the direction of air flow, it will be apparent that, in a blower formed in accordance with the manner illustrated, substantially all of the air passes therethrough in a direct continuous curvature. It is true, that the fishtail portion of the propeller permits some of the air to follow a reverse curvature, and as stated heretofore, this is not-desirable, but attention is invited to the fact that the air which travels in a reverse curvature forms only a small percentage of the air stream, as the area of the propeller hub portion is, as a rule, only from 1/9 to 1/6 of the total area of the air stream.

From the foregoing, it will be apparent that it is generally necessary, in order to effect the required velocity. pressure conversion, to so form the blower casing that the airtravels in a somewhat arcuate path, that is, inwardly toward the longitudinal axis of the blower on the inlet side of the blower and thence outwardly from the axis of the blower on the discharge side of the propeller: I have, therefore, established a formula by which this'arcuate airpassageway may be so proportioned that the best flow characteristics are assured.

Referring now to prime mover apparatus, such as steam turbines, and particularly to the blading therefor, it will be seen in Fig. 3 that the motive steam traverses the face of the one blade and the back of the adjacent blade in a somewhat arcuate path, much in the manner of the flow of air through the converging-diverging casing of a force draft blower. Referring now to Fig. 4, 30 and 31 represent conventional turbine blades of the impulse type, the steam traversing the space intervening between the working or front face 33 of the blade 30 and the rear or back face 34 of the blade 31, all as indicated by the arrow lines in Fig. 3. The rotor of the turbine is consequently actuated in .a direction represented by the arrow. In this figure, R represents the radius of curvature of the face of the blades and T represents the distance insteam tervening between the face of the blade 33 and the-back of the blade 34, or, in other words, the width of the flow passage. I originally established the fact that the best flow characteristics for turbine blading were obtainable when T was made to vary from 028R to 050R. This formula is now generally accepted by all turbine designers, and is fully and comprehensively set forth in Sterling s Marine Engineers Handbook, 1920 edition, pages 615 and 616.

it will, therefore, be apparent from the foregoing, that, in order to pass a fluid through a reversing passage or through a curved passage, best results are obtainable when the value R bears a certain definite relation to the value T. In turbine design, this idea is not solely applied to the blading, but to the design of the reversing chambers as well.

Referring now to Fig. 5, I show a turbine wheel 41 provided with suitable blades 42 and a nozzle block 43 for projecting steam at high velocities against the blades in order to rotate the wheel in the direction indicated by the arrow. in order that velocity energy of the steam may be more thoroughly ab- ,stracted, av reversing chamber 44, is frequently provided for receiving the steam after it is discharged from the turbine blades and for projecting it against the blades. In the reversing chamber-44, 45 to'49 inclusive, represent arcuate passageways taken by the in order to effect the: required reversal of direction. The design of reversing chamber shown in this illustration is a standard reversing chamber for a turbine of approximately 500 kw. capacity which is manufactured by the Westinghouse Elec. & Mfg. (10., the assignee of the present application. In this figure, R represents the radius of curvature of each passage and Tthe width of the passage in the same manner as the turbine blading previously referred to. From inspection of the dimensions given for this reversing chamber, it will be found thatthe R approximately .4. In other words, a value of R the design of reversing chambers, to give the most efficient flow characteristics.

I'have, therefore, conceived of the idea of applying the foregoing principle of design to blowers in order toreduce the losses involved in the passage of the air through the converging-diverging casing.

Returning now to Fig. 1, R represents the maximum radius of curvature of the air passing through the annulus formed between the central supporting member 25 and the casinglO while T represents the radial distance or width of air flow passageway intervening between the central supporting characteristic of each passage is approximating .4 has been found, in g lll lo. the lorm the value structure 25 and the casing 10.

ct blower illustrated in Fig. l,

should not exceed y i it will be seen that the value at when applied to blower design, is less than that tor turbine blading, the principal reason tor his being that edge losses seriously aid'ect he latter, while edge loss considerations do not enter into the design of a blower to the same entent. While l have shown term oil blower in which the hub portion ot the pro r, peller varies somewhat from the radius nevertheless t 18 apparent that l may so form t he blower that both the hub portion at the propeller and the central supporting member cooperate to define a continuous contour line substantially coinciding with the radius Under some conditions at installations, it may be absolutely necessary, as shown in 2, to discharge the air at a substantial angle with respect to the blower airis, in which. case the value ol 1% would, ordinarily be far in excess at Al. However, in such installations,

' good tlow characteristics may still he had by providing a series of intervening bathe members 51 and thus dividlng the air stream pass ing through the blower easing into several Fl! strata, each stratum'having a value at 4L! less than All The blower illustrated in Fig. 2 has been designed in accordance with this idea, the several passageways each having a till R flow characteristics are obtained, even though value ct less than .15. ln this way,ide'al I the requirements are such as to compel. rather i Fig. 2, and consequently the-flow is better.

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From the foregoing, it will he apparent thatvl have established certain basic or tundamental formulae for the design of the air passageway through blowers of the force draft type whereby the air passes through the blower with a minimum loss in kinetic enpropeller, and dctle erg-y. lln this l operating etliciency actor.

While l have shown my invention in two terms, it will be obvious to those the art, that it is o limited, hu' ceptible oil various o lications, without c thermal, and: l dos such limitations sl areiinposecl by the p cally set forth in the WV hat l claim is: l. ln a blower o .c combination oil a conve ing having an in propeller at or i supporting structu eluding a central. verges :lrrnn the pr lines with the hon passageway having o't axial direction the average thicltne not greater than ,l at curvature thereo 2. in a blower, th i having an air inlet ated in one diverging air outlet coated in the o a propeller disposer l. an interna tion or the casing,

erially improve the o. pparatus oil that char or art, or are 1 i r appended cla hroat portio for the propel,

her which. dir or d and i t ll do at divergen' r 'abstantial. not ,LFJ discharge one portions, oil the on into plat; each at which.

in the diverging outl tor dividing said po.

curved passageways l'l value ol not greater than atwherein l the maximum radius at our 1 sageway and T is 1 sageway as include a rat ln testimony wher have hereunt uh- ,v II a scribed rny named n h day o ,7 vi 7: ,"L

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